1. Field of the Invention
The present invention relates to a system for assembling and fixing a coil for eddy current braking to a railway vehicle.
2. Description of the Prior Art
The inventor has described in his co-pending U.S. patent application Ser. No. 413,338, now U.S. Pat. No. 3,881,578, a process and a device for eddy current braking for vehicles or engines moving on magnetic metal rails where the wheels are also of magnetic metal.
Without entering into unnecessary details under the circumstances, it will be recalled succinctly that the braking device according to this patent includes essentially energizing windings mounted preferably around the lower half of the wheels of at least one pair of wheels coaxial with the axle of magnetic metal, a supply system for DC electric current to said windings enabling the generation, at an opportune moment, of a magnetic flux generating eddy currents which are efficient retarders in the wheels and the rails.
One of the major problems to be resolved in such an eddy current dynamic braking system is to be able to transmit the braking effects to the chassis or to the bogie.
One of the solutions proposed in the aforementioned prior patents of the inventor consists of constituting each coil by a winding of concentric turns of conducting metal, preferably strips of oxidized aluminum so as to form, by gluing together, a rigid ring whose rigidity is due to the conducting metal itself. This rigid ring is then made fast to the chassis or the armature of the bogie by fixed fasteners, on the one hand, only at each of the ends of the winding, on the other hand, to the chassis or to the armature. More especially, the fasteners fixed to the ends of the winding are constituted by an upper part and by a lower part forming a sandwich of said winding, with the interposition of a thickness of elastic material, said upper and lower support parts being coupled together by fastening bolts.
If this solution is found to be perfectly suitable for use under conditions of use for which the heating would not be too great, it does not perfectly resolve the problem of longitudinal expansion of the coil for considerable heating for example of the order of 200.degree. C., without transmitting exaggerated forces to the assembly. Neither does this solution solve the problem of the thermal restraint of an aluminum coil held in a sandwich in steel supports.
It would have been possible to imagine the conventional solution consisting of interposing, between the support parts and the chassis or the bogie, known elastic means such as flexible mountings or the like.
This solution, in addition to its complexity, would besides resolve neither the delicate problem of the low frequencies characteristic of the assembly by reason notably of the further increased suspended mass, nor the problem of the contraction of the aluminum coil at low temperature with respect to that of the steel supports.
The solution proposed in the prior art patents have, in addition, other drawbacks which are less important among which may be mentioned:
the accumulation against the coil of mud or of water thrown by the wheel between the supports causing, by reason of the closeness of the metallic masses, insulation faults;
the presence of bolts and nuts which pose problems of safety;
the low mechanical stiffness of the assembly making risky the assembly in cantilever manner which is found to be however almost essential by reason of the design of the bogies themselves;
the double thermal barrier between the aluminum coil and the steel supports which makes worse cooling through the supports.
It is an object of the present invention to provide a system of assembly and fixing on a bogie or a chassis, a winding for dynamic braking by eddy currents, which completely eliminates the above-mentioned drawbacks of prior art systems.
It is another object to provide such a system which has complete fluid-tightness of the fastening between the winding and the supports ensuring good electrical insulation;
one-piece support parts, without nuts and bolts considerably increasing the safety whilst reducing the cost price;
great stiffness of these one-piece support parts enabling the mounting of the assembly on the chassis or the bogie as a cantilever system; and
a very distinctly improved cooling of the whole of the winding through a perfect thermal coil-support contact due to the increase of the surfaces and the reduction of thicknesses and the insulating homogeneity.